Light Diffusion Module and a Back Light Module Using the Same

ABSTRACT

A light diffusion module and a back light module using the same. The light diffusion module is disposed corresponding to the light source module of the back light module. The light diffusion module includes a first diffusion layer and the second diffusion layer. The first diffusion layer is disposed on top of the light source module and the top light exit surface has a plurality of first micro structures juxtapositioned to each other. The second diffusion layer is disposed on top of the first diffusion layer, and the top surface has a plurality of second micro structures juxtapositioned to each other. The ratio of the width of each first micro structure to the width of each second micro structure is between 1.1 and 1.8. The ratio of the height of each first micro structure to the height of each second micro structure is between 0.8 and 1.5

This application claims priority based on a Taiwanese patent applicationNo. 095102200 filed on Jan. 20, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a light diffusion module anda back light module using the same; particularly, the present inventionrelates to a light diffusion module applied in the liquid crystaldisplay panel and a back light module using the same.

2. Description of the Prior Art

The back light module has been widely applied to liquid crystal displaydevice, computer keyboard, mobile phone key, billboard, and otherdevices which need light source to provide the plain light source.Particularly, the market demands for the liquid crystal display deviceraise rapidly in recent years, the design of the back light moduleapplied to the liquid crystal display device becomes versatile in orderto fulfill the requirement of function and appearance.

However, when the back light module is applied to the liquid crystaldisplay panel, the uniformity of the light emitted from the back lightmodule plays a very important role that influences the overallefficiency of the liquid crystal display panel all the time. Especially,while the size of the liquid crystal display panel grows larger day byday, disposing the lamps of the module vertically downward has become atrendy development of the current back light module. How to uniformlydiffuse the light emitted from the lamps juxtapositioned to each otherand further preventing the condition of excessively bright orexcessively dark in certain areas become an important topic in designingthe liquid crystal display panel.

FIG. 1 a shows a conventional structure to diffuse the light. As FIG. 1a shows, the back light module 10 includes a plurality of lamps 13juxtapositioned to each other and a reflecting plate 15. There is alight controlling board 31 on top of the lamp 13, which functions asleading and controlling the path of the light. The light controllingboard 31 has a diffusion plate 32, which further diffuses the light. Ontop of the diffusion plate 32 is a liquid crystal glass 50. Afterrunning through the light diffusion simulation of the prior artstructure, the light diffusion effect is shown in FIG. 1 b. However asthe area within the dotted line in FIG. 1 b shows, it may be seen thatthose areas where lamps disposed tend to have the phenomenon of lightconcentration, and the darker parts of the weaker luminance area has thecontinuity as well.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light diffusionmodule to harmonize the light emitting from the light diffusion module.It is another object of the present invention to provide a lightdiffusion module to supply enough luminance of the emitting light. It isa further object of the present invention to provide a back light modulehaving more uniform light sourcing.

The present invention of the back light module includes a light sourcemodule and a light diffusion module. The light source module includes alight exit surface, wherein the light generated from the light sourcemodel 100 emits outwardly through the light exit surface. The lightdiffusion module is disposed corresponding to the light exit surface,includes a first diffusion layer and a second diffusion layer.

The first diffusion layer has a bottom light entrance surface and a toplight exit surface. The bottom light entrance surface is disposedcorresponding to the light exit surface of the light source module. Thetop light exit surface has a plurality of first micro structuresjuxtapositioned to each other. The first micro structure is preferredlinear, having a triangular cross-sectional area. In addition, the firstmicro structure is preferred to be formed on the first diffusion layerby an optical film manufacturing process.

The second diffusion layer is disposed on top of the first diffusionlayer, having a bottom surface and a top surface. The bottom surface isdisposed corresponding to the top light exit surface of the firstdiffusion layer, and the top surface has a plurality of second microstructures juxtapositioned to each other. The second micro structure ispreferred linear, having a triangular cross-sectional area. In addition,the second micro structure is preferred to be attached on the firstdiffusion layer.

The ratio of the width of each first micro structure to the width ofeach second micro structure is between 1.1 and 1.8. The ratio of theheight of each first micro structure to the height of each second microstructure 420 is between 0.8 and 1.5. Under such a design ratio, thelight diffusion module of the present invention may generate a betterlight diffusion effect and may have more uniform emitting light.Further, due to the enhancing effect of the first micro structure andthe second micro structure, it may not cause too much luminance losswhile the light passes through the first diffusion layer and the seconddiffusion layer.

In another embodiment, the light diffusion module further includes athird diffusion layer. The third diffusion layer is disposed between thefirst diffusion layer and the second diffusion layer and the Haze ispreferred over 80%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a prior art of the liquid crystal display panelstructure;

FIG. 1 b shows a simulation diagram of the light distribution whileapplying the structure of the embodiment shown in FIG. 1 a;

FIG. 2 is an explosive view of the embodiment of the back light moduleof present invention;

FIG. 3 is a sectional view of the embodiment shown in FIG. 2;

FIG. 4 is an explosive view of another embodiment of the presentinvention;

FIG. 5 is a sectional view of the embodiment shown in FIG. 4;

FIG. 6 is a simulation diagram of the light distribution while applyingthe structure of the embodiment shown in FIG. 4;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a light diffusion module and a back lightmodule using the same. In a preferred embodiment, the back light moduleis provided for the use of a liquid crystal display (LCD) panel. Inanother embodiment, however, the back light module may be also providedfor the use of a PC keyboard, mobile phone keys, billboards and otherdevices which need plane light source. Furthermore, the presentinvention further includes a liquid crystal display panel using thelight diffusion module. In the preferred embodiment, the liquid crystaldisplay panel includes a color liquid crystal display panel. However inanother embodiment, the liquid crystal display panel of the presentinvention includes a mono liquid crystal display panel. The liquidcrystal display device broadly refers to any display device using theliquid crystal panel, which includes a home LCD TV, LCD monitor for PCand laptop, liquid crystal display panel of mobile phone and digitalcamera.

As FIG. 2 shows, the back light module of the present invention includesa light source module 100 and a light diffusion module 300. The lightsource module has a light exit surface 110, preferably with a lamp 130and a reflecting plate 150. The light generated from the light sourcemodel 100 emits outwardly through the light exit surface 110. However inanother embodiment, the light source module 100 may adopt light fromother sources rather than the lamp 130, such as light emitting diode(LED).

As FIG. 3 shows, the light diffusion module 300 is disposedcorresponding to the light exit surface 110 and preferably is beingdirectly disposed on the light source module 100. The light diffusionmodule 300 mainly includes a first diffusion layer 310 and a seconddiffusion layer 320. In the preferred embodiment, the first diffusionlayer 310 is made of Cyclo Olefin Polymer, (COP). However in anotherembodiment, the first diffusion layer 310 may be made of other organicmaterials, such as polyester, (PET) and polycarbonate, (PC), etc. In thepreferred embodiment, the second diffusion layer 320 preferably includesan optical film and is made of polyester, (PET). However in anotherembodiment, the second diffusion layer may be made of other organicmaterials, such as polycarbonate, (PC).

The first diffusion layer 310 has a bottom light entrance surface 311and a top light exit surface 313. The bottom light entrance surface 311is disposed corresponding to the light exit surface 110 of the lightsource module 100. The top light exit surface 313 has a plurality offirst micro structures juxtapositioned to each other. As the embodimentshown in FIG. 2, the first micro structures 410 is linear and disposedparallel to each other on the top light exit surface 313. However inanother embodiment, the first micro structures 410 may have otherdifferent pattern as well. In addition, as FIG. 3 shows, thecross-sectional area of the first micro structures 410 is preferredtriangular. However in another embodiment, the cross-sectional area ofthe first micro structures 410 may be semi-circular, polygonal or otherkinds of shapes.

The first micro structure 410 is formed on the first diffusion layer 310preferably by an optical film manufacturing process. The optical filmmanufacturing process mentioned here includes etching, photolithography,and deposition. However in another embodiment, the first microstructures 410 may be attached on the first diffusion layer 310 or byother approaches. In addition, the first micro structure 410 may be madeof the material the same as the first diffusion layer 310. However inanother embodiment, the first micro structure 410 may be made of othermaterial, such as polymethy methacrylate, (PMMA), too.

As FIG. 3 shows, the second diffusion layer 320 is disposed on top ofthe first diffusion layer 310. The second diffusion layer 320 has abottom surface 321 and a top surface 323, and the bottom surface 321 isdisposed corresponding to the top light exit surface 313 of the firstdiffusion layer 310. The top surface 323 has a plurality of second microstructures 420 juxtapositioned to each other. As the embodiment shown inFIG. 2, the second micro structures 420 is linear and disposed parallelto each other on the top light exit surface 323. However in anotherembodiment, the second micro structures 420 may have other differentpattern as well. In addition, as FIG. 3 shows, the cross-sectional areaof the second micro structures 420 is preferred to be triangular.However in another embodiment, the cross-sectional area of the secondmicro structures 420 may be semi-circular, polygonal or other kinds ofshapes.

As FIG. 2 shows, the first micro structure 410 and the second microstructure 420 is preferably disposed towards the same direction, inother words, the first micro structure 410 and the second microstructure 420 extend along the same direction. In addition, the firstmicro structure 410 and the second micro structure 420 is preferablydisposed parallel to the direction of the lamp 130.

The second micro structure 420 is preferred to be attached on the firstdiffusion layer 310. However in another embodiment, the second microstructure 420 may be integrated on the second diffusion layer 320 by anoptical film manufacturing process or by other approaches. The opticalfilm manufacturing process mentioned here includes etching,photolithography, and deposition. Further, in the preferred embodiment,the second micro structures 420 may be made of polymethy methacrylate,(PMMA). However in another embodiment, the second micro structures 420may be made of the material the same as the second diffusion layer 320or other different material.

As FIG. 3 shows, the first micro structure 410 has a first width P₁ andthe second micro structure 420 has a second width P₂. The ratio of thefirst width P₁ to the second width P₂ is between 1.1 and 1.8. In otherwords, the first width P₁ is 1.1 to 1.8 times wider than the secondwidth P₂. In the preferred embodiment, the first width P₁ is between 65μm and 75 μm and the second width P₂ is between 48 μm and 52 μm. Undersuch a design ratio, the light diffusion module of the present inventionis able to provide a better light diffusion effect and more uniformlight sourcing.

In the preferred embodiment, each of the first micro structure 410 hasan equivalent first width P₁. However in another embodiment, the widthof each first micro structure 410 is unnecessarily the same as otherfirst micro structure 410. That is, not all the first micro structures410 have the first width P₁. Certain first micro structure 410 has athird width P₃ different from the first width P₁. Still, the ratio ofthe third width P₃ to the second width P₂ is between 1.1 and 1.8.

Similarly, in the preferred embodiment, each of the second microstructure 420 has an equivalent second width P₂. However in anotherembodiment, the width of each second micro structure 420 isunnecessarily the same as other second micro structure 420. That is, notall the second micro structures 420 have the second width P₂. Certainsecond micro structure 420 has a fourth width P₄ different from thesecond width P₂. Still, the ratio of the first width P₁ to the fourthwidth P₄ is between 1.1 and 1.8.

As the preferred embodiment shown in FIG. 3, each of the first microstructure 410 has a first height H₁, and each of the second structure420 has a second height H₂. The ratio of the first height H₁ to thesecond height H₂ is between 0.8 and 1.5. In other words, the firstheight H₁ is between the ranges of 0.8 to 1.5 times of the second heightH₂. Further, in another preferred embodiment, the first height H₁ isbetween 22 μm and 26 μm and the second height H₂ is between 23 μm and 27μm.

In the preferred embodiment, each of the first micro structure 410 hasan equivalent first height H1. However in another embodiment, the heightof each first micro structure 410 is unnecessarily the same as otherfirst micro structure 410. That is, not all the first micro structures410 have the first height H₁. Certain first micro structure 410 has athird height H₃ other than the first height H₁. Still, the ratio of thethird height H₃ to the second height H₂ is between 0.8 and 1.5.

Similarly, in the preferred embodiment, each of the second microstructure 420 has an equivalent second height H₂. However in anotherembodiment, the height of each second micro structure 420 isunnecessarily the same as other second micro structure's 420. That is,not all the second micro structures 420 have the second height H₂.Certain second micro structure 420 has a fourth height H₄ other than thesecond height H₂. Still, the ratio of the first height H₁ to the fourthheight H₄ is between 0.8 and 1.5.

As the embodiment shown in FIG. 3, the light enters the first diffusionlayer 310 from the bottom light entrance surface 311 of the firstdiffusion layer 310 after emitting from the light exit surface 110 ofthe light source module 100. As soon as the light processed by the firstmicro structure 410 emits from the top light exit surface 313, it entersthe second diffusion layer 320 and becomes a harmony light source afterprocessed by the second micro structure 420. In addition, due to theenhancing effect of the first micro structure 410 and the second microstructure 420, it may not cause too much luminance loss while the lightpasses through the first diffusion layer 310 and the second diffusionlayer 320.

FIG. 4 and FIG. 5 shows another embodiment of the present invention. Inthe embodiment, the light diffusion module 300 further includes a thirddiffusion layer 330. The third diffusion layer 330 is disposed betweenthe first diffusion layer 310 and the second diffusion layer 320. Thatis, before entering the second diffusion layer 320, the light will enterthe third diffusion layer 330 after emitting from the top light exitsurface 313 of the first diffusion layer 310. After processed by thethird diffusion layer 330, the light enters the second diffusion layer320 from the third diffusion layer 330.

The Haze of the third diffusion layer is preferred over 80%. In thepreferred embodiment, the third diffusion layer 330 has a plurality ofmicro molecule structures, making the third diffusion layer to haveenough Haze to produce the diffusion effect. In the preferredembodiment, the third diffusion layer 330 is an optical diffusion film,made of polyester, (PET). However in another embodiment, the thirddiffusion layer 330 may be made of other organic material, such aspolycarbonate, (PC) etc.

FIG. 6 shows a simulation diagram of the light distribution fromapplying the structure of the embodiment shown in FIG. 4 and FIG. 5,wherein the dark area is the area with weaker light while the shallowarea is the area with stronger light. As FIG. 6 shows, the shallow areahas already been uniformly diffused, and crossly mixed with the darkarea without any extra concentrating condition. From the above, it isknown that the light emitted from the lamp 130 in the light sourcemodule 100 has already been uniformly diffused, in other words, thelight diffusion module 300 has the characteristic of a better harmonylight distribution compared to the prior art.

In addition to raising the uniformity of the light source, the luminanceof the light will not be seriously affected. Taking the embodiment shownin FIG. 4 and FIG. 5 as an example, when the embodiment is applied inliquid crystal display panel, such as the panel of 32 inches, it willneed no more than twelve lamps 130 to set in the light source module 100to reach the luminance of 400 cd/M² (NIT), even to the standard of 500NIT. In the embodiment of the 37 inches panel, it will need no more thanfourteen lamps 130 to reach the same NIT. As to the panel sized from 45inches to 47 inches, no more than twenty lamps 130 are needed to set inthe light source module 100 to reach the same NIT.

Although the preferred embodiments of the present invention have beendescribed herein, the above description is merely illustrative. Furthermodification of the invention herein disclosed will occur to thoseskilled in the respective arts and all such modifications are deemed tobe within the scope of the invention as defined by the appended claims.

1. A light diffusion module for use with a back light module,comprising: a first diffusion layer including a bottom light entrancesurface and a top light exit surface, wherein said top light exitsurface has a plurality of first micro structures juxtapositioned toeach other, at least a part of said first micro structures have a firstwidth; and a second diffusion layer disposed above said first diffusionlayer, including a bottom surface and a top surface, wherein said bottomsurface is disposed opposite to said top light exit surface of saidfirst diffusion layer, said top surface has a plurality of second microstructures juxtapositioned to each other, at least a part of said secondmicro structure have a second width; wherein a ratio of said first widthto said second width is between 1.1 and 1.8.
 2. The light diffusionmodule of claim 1, wherein said first width is between 65 μm and 75 μm.3. The light diffusion module of claim 1, wherein said second width isbetween 48 μm and 52 μm.
 4. The light diffusion module of claim 1,wherein at least a part of said first micro structures have a thirdwidth different from said first width, the ratio of said third width tosaid second width is between 1.1 and 1.8.
 5. The light diffusion moduleof claim 1, wherein at least a part of said second micro structures havea forth width different from said second width, the ratio of said firstwidth to said forth width is between 1.1 and 1.8.
 6. The light diffusionmodule of claim 1, wherein said first micro structure has a firstheight, said second micro structure has a second height, the ratio ofsaid first height to second height is between 0.8 and 1.5.
 7. The lightdiffusion module of claim 6, wherein said first height is between 22 μmand 26 μm.
 8. The light diffusion module of claim 6, wherein said secondheight is between 23 μm and 27 μm.
 9. The light diffusion module ofclaim 6, wherein at least a part of said first micro structures have athird height different from said first height, the ratio of said thirdheight to said second height is between 0.8 and 1.5.
 10. The lightdiffusion module of claim 6, wherein at least a part of said secondmicro structures have a forth height different from said second height,the ratio of said first height to said forth height is between 0.8 and1.5.
 11. The light diffusion module of claim 1 further comprising athird diffusion layer, disposed between said first diffusion layer andsaid second diffusion layer, wherein a Haze of said third diffusionlayer is over 80%.
 12. The light diffusion module of claim 11, whereinsaid third diffusion layer is made of Polyester, (PET).
 13. The lightdiffusion module of claim 1, wherein said first micro structure and saidsecond micro structure are disposed along the same direction.
 14. Thelight diffusion module of claim 1, wherein said first diffusion layerincludes a diffuser plate disposed on said light diffusion module. 15.The light diffusion module of claim 1, wherein the material of saidfirst diffusion layer is made of Cyclo Olefin Polymer, (COP).
 16. Thelight diffusion module of claim 1, wherein said first micro structure isattached to said first diffusion layer.
 17. The light diffusion moduleof claim 1, wherein said first micro structure is formed on said firstdiffusion layer by an optical membrane manufacturing process.
 18. Thelight diffusion module of claim 17, wherein said optical filmmanufacturing process includes an etching process.
 19. The lightdiffusion module of claim 17, wherein said optical film manufacturingprocess includes a lithography process.
 20. The light diffusion moduleof claim 1, wherein said first micro structure is made of Polymethylmethacrylate, (PMMA).
 21. The light diffusion module of claim 1, whereinsaid second diffusion layer includes an optical thin film.
 22. The lightdiffusion module of claim 21, wherein the material of said optical filmis selected from a group of Polyester, PET, Polycarbonate, PC and anycombination therefrom.
 23. The light diffusion module of claim 1,wherein said second micro structure is attached to said second diffusionlayer.
 24. The light diffusion module of claim 1, wherein said secondmicro structure is formed on said second diffusion layer by an opticalfilm manufacturing process.
 25. The light diffusion module of claim 24,wherein said optical film manufacturing process includes an etchingprocess.
 26. The light diffusion module of claim 24, wherein saidoptical film manufacturing process includes a lithography process. 27.The light diffusion module of claim 1, wherein said second microstructure is made of Polymethyl methacrylate, (PMMA).
 28. The lightdiffusion module of claim 1, wherein said first micro structure has atriangular cross section.
 29. The light diffusion module of claim 1,wherein said second micro structure has a triangular cross section. 30.A back light module, comprising: a light source module, having a lightexit surface; and a light diffusion module of claim 1 disposedcorresponding to said light exit surface.
 31. A liquid crystal displaydevice using the light diffusion module of claim 1, wherein said liquidcrystal display device is selected from a group of liquid crystal TV,liquid crystal monitor, liquid crystal display panel of mobile phone andliquid crystal display panel of digital camera.